The overall aim of this research is to continue the quest toward understanding the development of social-affective expressions during infancy. A guiding point of view is that the development of affect can be understood more clearly if data of CNS maturation, the infant's environment, and his behavior, are obtained concurrently. A group of short-term studies, mainly cross-sectional, will test questions related to affect expressions and physiological state, and the development of sleep and wakefulness. Normal infants will be studied by means of naturalistic observations in the home, and a variety of experimental approaches in both home and laboratory. Wherever possible, relations between naturalistically-observed behaviors and physiological concomitants (including EEG, respiration, electro-oculogram, muscle tone, and heart rate) will be sought. A longitudinal study seeks to establish correlates between CNS maturation and development of affective behaviors in individual infants followed from before birth through the first postnatal year. The study will employ both the design and comparison data from a previous longitudinal study of normal infants. Subjects for the proposed study will be infants with Down's syndrome, with X-chromosome abnormalities, and battered infants. It is postulated that alterations in normative sequences of social-affective development, and CNS development, will be found in the abnormal infants. It is anticipated that such findings will increase the understanding of normal developmental processes and ultimately may lead to preventive health measures in the abnormal group.